1. Field of the Invention:
The present invention relates to a molded gypsum product which has a low average apparent bulk density of 0.3 to 0.9 g/cc and has high strength and a process for preparing the same.
2. Description of the Prior Art
Recently, a large amount of gypsum has been produced as by-products from waste gas desulfurization processes etc., From the viewpoints of environmental pollution and effective ulitization of sources, uses of the by-product gyspum in the fields of constructions, building materials and other industrial materials have been studied.
Thus, molded gypsum products have low strength as the single component product and have been improved to increase the strength by incorporating fiber reinforcing materials or by compression molding to form high density product.
When the gysum product are used as construction materials such as fire protection materials of steel frame structural parts of buildings or fire resistant partition wall for medium and high-rise buildings, light weight as well as high strength for required. Such reduction in weight of a gypsum product can be attained by imparting porosity to the product. The strength of the molded product having light weight and high strength.
Britifh Pat. No. 1,204,541 discloses the method of making fiber reinforced plaster wherein a mixture prepared by dispersing glass fiber in a slurry of hydraulic gypsum is fed in a mold and water was discharged from the mixture by compressing it to lower the water/plaster ratio to a value approaching but not below the minimum required to hydrate the plaster.
However, in the method, the strength of the molded product is increased by increasing the density at the sacrifice of weightlightening of the molded product, whereby the apparent bulk density of the molded product is remarkably high as 1.4 to 1.9 g/cc.
U.S. Pat. No. 3,862,881 discloses the molded lamellar gypsum products made of dihydrated gypsum having lamellar structure. In this patent, a molded product in produced by setting a hydraulic gypsum with water in a mold under pressure while removing excess water for setting, whereby the apparent bulk density of the molded product is as high as 1.5-2.2 g/cc.